The photovoltaic power generation is widely performed as an effective power generation system that utilizes natural energy. However, in order to perform the photovoltaic power generation, a wide light receiving surface is needed. Therefore, in order to utilize such a wide area more effectively, another value added to the photovoltaic power generation is considered. As an example of such an added value, it is proposed that a hot-water supply system is added to a photovoltaic power generation system. (refer to Patent Documents 1 and 2).
FIG. 6 is an erecting sectional view illustrating a conventional solar system disclosed in Patent Document 1. In the solar system disclosed in Patent Document 1, some panels of solar panels 100 arranged on a roof R or the like are selected; solar hot-water panels 110 including heat collecting pipes 120 and a heat insulation 130 are disposed on only a lower side of the selected panels. Therefore, a following effect is achieved: it is possible to arrange the solar hot-water panels 110 at the optimal positions. However, since the solar panel 100 and the solar hot-water panel 110 are separately manufactured, it is not possible to use an existing frame 150 of the solar panel 100 as is. In other words, since a base 160 of the solar hot-water panel 110 needs to be separately disposed, installation work of the panels is complicated.
FIG. 7 is an assembling diagram of an integrally formed photovoltaic thermoelectric hot-water panel disclosed in Patent Document 2. Since the photovoltaic thermoelectric hot-water panel disclosed in Patent Document 2 has a structure in which the solar panel 100, the heat collecting pipes 120, and the heat insulation 130 are all integral, the following effect is achieved: it is possible to install a panel having two functions in the conventional frame.
However, in Patent Document 2, the following points still haven't been considered. The heat collecting pipe 120 needs to have corresponding water-pressure resistance performance and long-term durability, and it is difficult to supply sufficient hot water throughout a year when heat storage properties, the strength of the entire panel, or the like is not sufficiently considered.
Further, the conventional hybrid panel has a combined configuration of a heat absorbing sheet and copper pipes in a portion of the panel on a back side of the photovoltaic module, and produces hot water through “heat conduction”. In order to reduce heat release from hot water warmed through the copper pipes, the conventional method employs a structure of enclosing the copper pipes and the photovoltaic module with the heat insulation. However, due to a heat retention effect, the temperature of the hybrid module rises to about 100 degrees Celsius. In addition, even though water passes through, a product has a higher temperature than a normal panel, and the high temperature leads to deterioration in power generation performance and a decrease in the service life of the product.    [Patent Document 1] Japanese Unexamined Patent Publication No. 2013-2709    [Patent Document 2] Japanese Unexamined Patent Publication No. 2000-241030